A gas turbine engine is typical of turbine machines in which the concepts described herein may be advantageously employed. In a gas turbine engine such as the type employed in powering aircraft, pressurized air and fuel are burned in a combustion chamber to add thermal energy to flowing through the engine. The effluent from the combustion chamber comprises high temperature products of combustion which are flowed downstream in an annular flow path through the turbine section of the engine. Nozzle guide vanes at the inlet to the turbine direct the effluent onto a multiplicity of rotor blades which extend radially outward from the engine rotor. The nozzle guide vanes and rotor blades are particularly susceptible to thermal damage and are commonly cooled by air from the engine's compressor, which is bled through suitable conduits in the engine for subsequent distribution to the rotor blades and guide vanes.
A common method of cooling turbine blades and vanes utilizes impingement tubes or baffles disposed within the turbine blade or vane. The baffles extend through the airfoil portion of the turbine vane and is in fluid communication with the source of cooling fluid. The baffles are perforated with a plurality of impingement holes spaced about through which the cooling fluid passes. The cooling fluid exiting the baffle impinges upon the internal surfaces of the airfoil. The arrangement of impingement holes distributes the cooling fluid within the airfoil to prevent a deficiency in cooling from occurring in a particular location.
The thermal damage to which the turbine airfoils are susceptible, manifests itself in cracking and geometric distortion (twisting) of those components as well as breakdown (chipping) of the thermal barrier coatings thereon. Accordingly, throughout the life span of a gas turbine engine, these components must be periodically removed from the engine and overhauled. As part of such overhaul, the cooling baffles are removed prior to any repair and/or recoating of the interior airfoil surfaces. The baffles are removed typically, by tapping the baffle with a punch or the like from one end thereof, thereby dislodging the baffle and sliding the baffle out of the airfoil through the opposite end thereof. Another known practice of the baffle removal involves gripping an edge of the baffle with pliers or a similar gripping device and pulling the baffle out through one end of the airfoil. In either case, the baffle is frequently damaged beyond repair. Indeed, in modern gas turbine aircraft engines, baffle scrap rates of 20%-100% are not uncommon. Inasmuch as the price of such baffles ranges from approximately $45.00 to approximately $400.00 each, such scrap rates add significantly to the cost of the overhaul and repair of these components and thus, the operation of the engines in which they are employed.